Piezoelectric thin film resonator
a thin film resonator and piezoelectric technology, applied in the direction of piezoelectric/electrostrictive/magnetostrictive devices, electrical apparatus, impedence networks, etc., can solve the problems of reducing filter bandwidth, vibration part of floating portion liable to warp, and reducing filter strength, so as to ensure the strength of the membrane without degrading the resonant properties, high reliability
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example 1
[0081]FIG. 1 is a plan view schematically showing an important portion of the structure of a piezoelectric thin film resonator 10 according to Example 1. FIG. 2 is a cross-sectional view cut along the line II-II in FIG. 1.
[0082]The piezoelectric thin film resonator 10 has the structure that a dielectric film 16, a lower electrode 17a, a piezoelectric thin film 18, an upper electrode 17b, and reinforcing films 19a and 19b are formed on a substrate 11. Since an airspace layer 14 (see FIG. 2) formed by removing a sacrifice layer 13 (see FIG. 1) present between the substrate 11 and the dielectric film 16, a vibration part 12 has a structure which floats over the substrate 11. The vibration part 12 is formed by the dielectric film 16, the electrodes 17a and 17b overlapped with each other in lamination direction, and the piezoelectric thin film 18 between the lower electrode 17a and the upper electrode 17b.
[0083]The piezoelectric thin film resonator 10 is formed as described below.
[0084]...
example 2
[0095]FIG. 4 is a plan view schematically showing an important portion of the structure of a piezoelectric thin film resonator 30 according to Example 2. FIG. 5 is a cross-sectional view cut along the line V-V in FIG. 4.
[0096]The piezoelectric thin film resonator 30 has the structure, which is approximately equivalent to that in Example 1, in which a dielectric film 36, a lower electrode 37a, a piezoelectric thin film 38, an upper electrode 37b, and reinforcing films 39a and 39b are formed on a substrate 31. By the presence of an airspace layer 34 formed between the substrate 31 and the dielectric film 36, it is a structure in which a vibration part 32 floats over the substrate 31. The vibration part 32 is formed by a region 32 in which the electrodes 37a and 37b are overlapped with each other in the laminating direction and the vibration part 32 being composed of parts of the dielectric film 36, the lower electrode 37a, the piezoelectric thin film 38 and the upper electrode 37b.
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example 3
[0101]FIG. 6 is a plan view schematically showing an important portion of the structure of a piezoelectric thin film resonator 40 according to Example 3.
[0102]The piezoelectric thin film resonator 40 has the structure which is approximately equivalent to that in Example 1; however, different from Example 1, two resonator elements are provided. That is, a dielectric film 46, a lower electrode 47a, a piezoelectric thin film 48, an upper electrode 47b and 47c, and reinforcing films 49a, 49b, 49c, 49d, and 49s are formed on a substrate. By the presence of an airspace layer formed by a sacrifice layer 43 provided between the substrate and the dielectric film 46, it is a structure that vibration parts 42s and 42t float over the substrate, the vibration parts 42s and 42t are formed by the dielectric film 46 in regions 42s and 42t that the lower electrode 47a is overlapped with the upper electrodes 47b and 47c and the piezoelectric thin film 48 in the laminating direction. The reinforcing f...
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